1. Field of the Invention
This invention relates to a process for manufacturing shutter screen blades to be used for a focal plane shutter and a lens shutter or the like and more particularly to a process involving coating and press operations in forming the shutter blades of a focal plane shutter with a metal plated thin plastic sheet material.
2. Description of the Prior Art
In camera equipment, there has existed a need to increase shutter speed and to reduce the load on a motor drive arrangement by reducing the weight of the blades forming shutter screens in focal plane shutters in general. To meet this requirement, the present applicant has previously proposed in Japanese utility model application No. 55-6900 a focal plane shutter in which the shutter screen blades are formed with a plastic material, with the plastic shutter screen blades thus formed being plated with a metal and assembled into a focal plane shutter as shown in FIG. 1 of the accompanying drawing. The structural arrangement of the focal plane shutter is as follows:
FIG. 1 shows the leading screen of the focal plane shutter as having come to a middle point of an aperture. The aperture is provided in a shutter base plate 1 and is arranged to be opened and closed by leading and trailing shutter screens. The trailing shutter screen is composed of constituent blades 4, 5, 6, 7 and 8. Each of the blades is attached to a trailing screen driving arm 2 having a trailing screen driving pin 17 and to a trailing screen auxiliary arm 3 through supporting pins. Further, each of the constituent blades 12, 13, 14, 15 and 16 of the leading shutter screen is attached to a leading screen driving arm 10 having a leading screen driving pin 18 and to a leading screen auxiliary arm 9 through supporting pins respectively. When forces are transmitted to the leading screen driving pin 18 and to the trailing screen driving pin 17 from driving sources which are not shown, the leading and trailing shutter screens are moved by them in parallel with the aperture in such a way as to effect an exposure.
In a focal plane shutter of this type, the shutter screen blades must also have adequate flatness for enhancement of the travelling performance of the shutter screens and for ensuring light shielding capability in addition to the above stated need for reduction in weight. Therefore, in forming these shutter screens with a plastic material to meet the requirement first mentioned in the foregoing, the shutter screen blades must be formed with a flat configuration.
According to conventional methods for manufacturing shutter screen blades, each blade is prepared by coating it after it is obtained from a plastic thin sheet like material by punching the material to form the blade contour. Therefore, when the obverse and reverse surfaces of each screen blade are either coated with different coating materials or separately coated in accordance with the conventional method, the blade tends to warp as shown in FIG. 7. Since blades deformed in such a manner are hardly usable as shutter screen blades for focal plane shutters for reasons as mentioned in the foregoing, they must be rejected. The rejection due to such warping thus has been causing an increase in the cost of shutter screen blades. Besides, since each blade is completely punched out of a plastic thin sheet material with a press operation applied to the entire contour thereof before coating, these blades tend to be scattered by air pressure used in spraying a coating material thereon. In accordance with the conventional method, therefore, it has been difficult to have shutter screen blades efficiently manufactured.